This invention generally relates to a computer system using a disk based operating system and more specifically addresses operation of a client computer running real-time programs among its plurality of programs while in a computer network where the client computer uses a disk based operating system but does not have a local hard disk and relies on a remote host computer to initially provide disk based operating system information.
FIG. 1 illustrates a known computer network 10 that includes a host computer 12 connected by a communication network 14 to a plurality of client computers 16. The communication network 14 may comprise an Ethernet network or a network running a form of Internet Protocol communications. The client computers 16 in a typical application will include a microprocessor utilizing a disk based operating system supported by random access memory and a disk for non-volatile storage, e.g. typically a hard drive. Each client computer is booted initially based on information contained in the disk based operating system contained on its local hard drive. In this environment each client computer operates substantially as a stand-alone computer that includes communication capabilities with the host computer 12 and other client computers. Such client computers place a relatively low traffic load on the communication network 14 for information essential for operation of each client computer since each contains its own operating system.
Another environment with the same physical configuration as shown in FIG. 1 is based on client computers that do not have a local hard drive. In this environment each client computer includes a network bootable component permitting the client computer to communicate with the host computer and load all of the necessary operating system elements from the host computer into random access memory at the client computer. In this configuration each client computer relies upon the continuous availability of communications with the host computer through the communication network to obtain new or refreshed operating system information as required. This causes a substantial amount of traffic on the communication network since many maintenance and application tasks running at the client computer require operating system access and/or updating. Such loading is exacerbated when the client computer functions in a real-time operating mode and as the number of client computers increase. As such loading continues to increase, either the processing capabilities of the host computer or the communication throughput of the communication network will become exhausted and will lead to a crash of one, if not all, of the client computers. Even if such loading does not totally exhaust the capabilities of the host computer or the communication network, excessive loading can cause the response times to be larger than can be tolerated by the client computers and will also lead to crashes of the client computers. There exists a need for a solution to such problems.